Why Does My DE Filter Lose Pressure

[SunnyOptimism]

Sorry, I wanted to reply sooner but yesterday fell apart on me so I just couldn't get to it.

First off, properly cleaning a DE filter takes a lot of time. It takes me a good 4 hours to clean mine so I know how you feel.

OK, here's where I'll talk cleaning and recharge procedure. I realize our two DE filters are different internally but I think the process is the same. You mentioned adding 12 cups of DE to a bucket and then pouring that into the skimmer. So that brought up questions in my mind -

Are you truly adding 12 cups (as in a standard 8oz cup) of DE? Do you know what that is in weight as DE filters typically require a starter charge (full charge after cleaning out old DE) that is measured in pounds?

I use a orange plastic DE scoop that I got from the pool store. It is larger than a standard coffee can. It is designed to roughly hold enough DE to equal ~ 1/2 pound (DE has a very low weight to volume ratio). My QuadDE-100 requires a 10lbs starter charge and then 2-3 lbs per backwash. Here's my procedure for starting the filter after a full clean out -

1. Run the pump on high speed and set valves so that all of the suction is on the skimmer
2. Mix 1-2 scoops of DE into a 5 gal bucket of pool water and keep in suspension as best as you can

3. VERY SLOWLY (while keeping the DE stirred) add the DE to the skimmer. Try to take 30sec to 1 min to empty bucket

4. Repeat steps 2-3 until 10lbs (20 scoops) of DE is added.

5. Note filter pressure (my clean system pressure at low speed is typically 10-11PSI)

6. Leave filter running at high speed for a minimum of 1 hour. Set back to normal speed and run the pump for a minimum of 8-12 hours. DO NOT ALLOW THE PUMP TO SHUT OFF DURING THIS TIME.

7. Reset all pumps speeds and valves to standard operating positions and note clean filter pressure. If it's not at the typical pressure, add some extra DE as-needed.

So the reason why I follow this VERY SLOW start procedure is this - DE settles out of suspension in water fairly quickly. You can see it by mixing DE in your bucket and watching it. Within 30-60sec, the DE mostly settles on the bottom. The settling time is shorter the more DE you have in suspension. Therefore, if you load up a huge charge of DE into a small volume of water, it can very easily settle in your pipes rather than make it all the way to the filter. I use my pumps high speed to ensure that the DE gets sucked as rapidly as possible to the filter so that the turbulence ensure that the DE reaches the cartridges.

When you opened your DE filter, you must have noticed all the DE piled up like beach sand in the bottom of the filter. For the most part, a lot of your DE sits on the bottom of the filter an only a small fraction of it coats the grids (or cartridges in my filter). Thereofore, when you start up your filter you want to make sure the DE gets to the grids and stays there. That is also the reason for letting the pumps run for a long time afterwards. You want to make sure the DE embeds onto the grid material so it stays there.

The weird fact about DE filters is that they work better when the DE is a little "dirty" as opposed to fresh. The "dirt" and "gunk" helps keep the DE plastered onto the grids. Fresh DE charges have a tendency to slough off the grids when you turn the pumps off and thus uncovers the mesh. Then, when you start up, the DE gets mixed up with water and re-coats the grids. This is also the reason why on a fresh DE charge, you'll see what looks like dirty water coming out of your returns for 30secs or so after turning on the pump. That arises from the fact that there are areas of your grids that are not initially coated with DE and so the "dirty water" gets through. Once those areas clot up with DE, the filter starts working normally.

As for your sudden pressure rise, I have seen that too on my system. As I'm charging the DE into a cleaned filter, the pressure gauge barely budges. Then, on that last bucket of DE, the pressure rapidly spikes up. It could be that you have excess DE in your lines somewhere and, over time, the pressure spikes up as the grids become fully coated.

If you're experiencing a high system pressure and loss of prime in the pump, that could be a symptom of too much DE in the filter.

Let me know what you think.

[gkrupkin]

First, thank you for taking the time to help me. You are correct, I"m using a red 16oz cup. I've already ordered a DE Scoop cup last night. For now, is there an easy to way to figure out how much DE i need using my plastic cup?

Also, how do I run the pump on high speed? I know there are main drains and skimmer drains. I do have 2 pipes coming into my pump and 2 going back out. But they are not labeled. I assume I need to shut off the main drain and do only skimmer and that would run my pump on high speed? I'm trying to insert a pic but I can't figure out how.

[FormerBromineUser]

How is it going?

[gkrupkin]

turns out it must have just been a dirty pool. Pressure seems to hold steady at 20psi now. Lesson learned here though is that a dirty pool may require a backwash every 2 hours or so. Seems to be pretty normal.